Combined hydrodesulfurization and reforming process



July 7, 1959 Filed March 22, 1954 i c. H. o. BERG COMBINEDHYDRODESULFURIZATION AND REFORMING PRO CESS COMBINEDHYDRODESULFURIZATION AND REFORMING PROCESS Clyde H. O. Berg, Long Beach,Calif., assignor to Union Oil Company of California, Los Angeles,Calif., a corporation of California Application March 22, 1954, SerialNo. 417,569

9 Claims. (Cl. 208-99) This invention relates to an improved process andapparatus for the continuous treating or contacting of fluids with arecirculating stream of solid granular contact material and inparticular relates to the conversion of petroleum and other hydrocarbonsin the presence of a recirculated stream of granular hydrocarbonconversion catalyst. In its most specific embodiment this inventioncontemplates an improved combination process and apparatus for thesimultaneous treatment of two hydrocarbon fractions of substantiallydifferent properties, such as the catalytic reforming of naphtha orgaso- I'line fractions and the catalytic desulfurization,denitrogenation, and deoxygenation of the reformed naphtha :and agas-oil fraction in the presence of a special catalyst which hasreforming, desulfurization, denitrogenation and 'deoxygenation activityand in which the hydrocarbon conversions cooperate with one another inan integrated process of increased efiiciency.

The prior practice in hydrocarbon oil refining includes many catalyticoperations wherein hydrocarbon fractions are treated and converted in avariety of processes to improve various physical and chemical propertiesthereof. Many hydrocarbon fractions contain undesirable impurities inthe form of hydrocarbon derivatives of "sulfur, nitrogen, and oxygenwhich render them unfit .for their intended uses such as cracking stock,internal combustion engine fuels, and the like. In addition, the naphthaor gasoline fraction of these hydrocarbons con 'tain insuificientquantities of hydrocarbon types having high antiknock characteristicsand extensive refining operations are effected to increase the quantityof aromatic :and branched chain hydrocarbons in these gasoline fractionsto make them suitable for use as fuels in high compression engines.Accordingly, modern refining practice tends more and more towardcatalytic treatment of such hydrocarbon fractions to remove undesirablefractions and to impart desirable characteristics thereto by suchspecific processes as catalytic desulfurization, catalyticdenitrogenation, and catalytic reforming which involve parafiinhydrocarbon isomerization, dehydrogenation and cyclization, andnaphthene hydrocarbon dehydrogenation to produce homologs of benzenewhich have high antiknock characteristics. The removal of hydrocarbonderivatives of oxygen, nitrogen and sulfur are required to produce asweet non-corrosive product having a high lead susceptibility and toavoid problems of corrosion.

The desulfurization and denitrogenation of the naphtha and gas-oilfractions of crude petroleum ordinarily require reaction temperaturesranging from about 575 F. to about 900 F., pressures between about 50psi. (pounds per square inch) to about 5000 p.s.i. in the presence of arecycled stream of hydrogen. The hydrocarbon compounds of sulfur,nitrogen, and oxygen are decomposed forming a hydrocarbon and eitherhydrogen sulfide, ammonia or water. In the reforming of lowgradegasoline fractions, the naphtha vapor is contacted with a reformingcatalyst attemperatures between about States Patent 2,893,945 PatentedJuly 7,

800 F. and about 1100 F. at pressures in substantially the same range asfor desulfurization, and in the presence of a hydrogen gas recycle.Although desulfurization, denitrogenation, and reforming all havedesirable beneficial effects upon low-grade gasoline, the differencebetween the optimum reaction temperatures of these processes and thefact that the hydrogen sulfide, ammonia, and water contaminate thehydrogen recycle stream employed in the first-named operation, haveheretofore necessarily required that these operations be effectedentirely separately under conditions requiring separate gas plants, andunduly complicated processing steps and apparatus.

It has been found that granular catalyst of the cobalt molybdate type,supported on activated alumina carriers and analyzing between about 2%and 10% by weight of cobalt oxide (C00) and between about 5% and about30% by weight of molybdenum trioxide (M003), is highly stable, rugged,and relatively inert to materials which conventionally poison reformingand desulfuriza' tion catalysts. It has also been found that catalystsof this type are simultaneously highly active in promoting the reactionsinvolved in hydrocarbon desulfurization, denitrogenation, deoxygenation,and reforming.

Accordingly, the present invention is directed to.a novel and highlyefiicient integrated process wherein lowgrade naphtha or gasolinefractions are catalytically reformed under optimum reforming conditionsand gasoil fractions are desulfun'zed and denitrogenated also at optimumreaction conditions simultaneously in a single contacting column ofunique design and in the presence of one granular catalyst consistingessentially of cobalt rnolybdate which is recirculated through thecolumn. By means of a particular scheme of simultaneous operation of thedesulfurizing and reforming zones in the contacting column, morespecifically defined below, it is found that there exists apparently anactive cooperation be.- tween the two operations whereby novel andunexpected results have been obtained and which are apparentlyunobtainable when the two operations are conducted separately.

It is therefore a primary broad object of the present invention toprovide a new and improved fluid-solids contact process.

It is a more specific object of this invention to provide an improvedintegrated hydrocarbon conversion process for the simultaneousdesulfurization and reforming in a single contacting column.

It is an additional object of this invention to provide in a singlecontacting zone a downwardly moving bed of granular cobalt molybdatecatalyst and in which contacting zone a naphtha fraction is reformed inthe lower portion thereof and then the reformed naphtha and acontaminated gas-oil fraction, containing hydrocarbon derivatives ofsulfur, nitrogen and/ or oxygen, are simulta neously treated in theupper portion of the contacting zone for the desulfurization,denitrogenation, and deoxy genation thereof.

It is a more specific object of this invention to provide in ahydrocarbon conversion process an improved contacting operation whereinthe moving bed of conversion catalyst is first passed into the upper endof the contacting Zone, then passed downwardly through a desulfurizationzone and, is then divided into two catalyst streams, one of which ispassed directly into and through a subjacent reforming zone and theother of which is passed downwardly through said reforming zone inindirect heat exchange relation thereto, and then the streams arecombined for passage through a subsequent stripping and reforming zone.

It is an additional object of this invention to provide in a hydrocarbonconversion process employing arecirculated solid catalyst stream a novelandimproved catalystelutriation step for solids fines removal, and anovel hydrogen pretreatment step which substantially eliminates from thereactor efiluent elemental sulfur and sulfur containing compounds.

It is also an object'of this invention to provide an apparatus foraccomplishing the aforementioned objects.

Other objects and advantages of this invention will becomeapparent tothose skilled in the art as the descriptionv thereof proceeds.

Briefly the present invention comprises an improved combination processfor the simultaneous desulfurization, denitrogenation, and deoxygenation(heretofore and hereinafter referred to collectively as desulfurization)of gas-oil and naphtha hydrocarbon fractions simultaneously with thereforming of the naphtha fraction in a single contacting column or zonewhich includes isolated and yet communicating desulfurization andreforming zones through which a moving bed of granular catalyst ispassed. Preferably the granular catalyst is of the cobaltimolydbate typereferred to above which has reforming and resulfurization activity. Thecontacting zone employed in the present invention is provided with adesulfurization zone in the upper portion and a reforming zone in .thelower portion and a moving bed of granular cobalt molybdate catalystpasses downwardly by gravity through each zone. The spent catalyst removed from the contacting .zone and containing a deactivatinghydrocarbonaceous deposit is recirculated to the top "of the contactingzone through a regeneration zone in which the hydrocarbonaceous depositis burned from the catalyst to restore its former activity.

The modification of this invention illustrated in the figure involvesthepassage of the entire catalyst stream downwardly as a moving bedthrough the desulfurization zone, .andlthen dividing thespent catalystinto a primary and a secondary. stream. The primary stream is thenintroduced directly into the reforming zone wherein it passes downwardlyas a moving bed and the other stream islpassed.downwardlyindirectlythrough and in indirect heat exchange relationship with the bed ofcatalyst in the major portion of the reforming zone. The two streams arecombined in the lower portion of the reforming zone to re-establish theentire catalyst stream which contacts the freshly introduced naphthareactant mixture for naphtha stripping. The spent catalyst is then steamstripped and removed from the system for regeneration. This modificationof the invention is especially well adapted to the desulfurization ofheavily contaminated gas oils requiring large amounts of hydrogensimultaneously with the reforming of relatively naphthenic gasolineswhich produce large quantities of hydrogen.

In the process of this invention, the endothermic reactionscharacterizing naphtha reforming and the exothermic reactions occurringduring desulfuriza-tion, denltrogenation and deoxygenation in thedesulfurization zone, normally result in the generation and maintenanceof temperature gradients if the reaction zones are permitted to operateadiabatically. Reforming reaction rates decrease significantly withrelatively small decreases in temperature and difliculty controllablehydrogenation reactions may occur if the temperature is permitted toincrease unduly in the desulfurization zone. Accordingly, in the presentinvention the reacting mixture of naphtha and hydrogen is preferablyheated at one or more points along the length of the reforming zone andthe reacting mixture of 'gasoil and naphtha vapor and hydrogen is cooledat one or more points along the length of the desulfurization zone tomaintain the average reaction temperature in each of said zonessubstantially uniform art the optimum value.

In the reforming zone of the process of the present invention, naphthavapor and between about 500 and 1.0,000 s. c.f. of hydrogen per barrelof naphtha are passed in contact with a cobaltmolybdate catalyst at aliquid hourly space velocity (L.H. S. V.) of between about 0.2 and 2.0,at temperatures between about 800 F. and 1000" F., preferably about 900F., and at a pressure of between 50 p.s.i. and 5000 p.s.i., preferablybetween about 50 and 1000 p.s.i. such as about 400 p.s.i. todehydrogenate and cyclize paraflin hydrocarbons and to dehydrogenatenaphthene hydrocarbons to produce a highly aromatic reformed gasolineproduct containing branched chain hydrocarbons and having a knock ratingof above 92. Heat is added along thelength of the reforming zone tomaintain a uniform temperature profile therein by means more fullydescribed below. The reformed naphtha and the recycle hydrogenstream,which now contains excess hydrogen produced during the reforming, ismixed with the gas-oil to be treated. The gasoil may be partly orcompletely vaporized, but in any event is preferably at a temperaturewhereby admixture with the efiluent from the reforming zone will producea mixture having a temperature of about 775 F., which is the optimumpreferred gas-oil and naphtha desulfurization temperature.

This mixture of gas-oil, naphtha and hydrogen is passed at the reducedtemperature of from about 575 F. to 900 F., at an L.H.S. V. betweenabout 0.2 and 15.0, at substantially the same pressure and with from 50to 5000 s.c.-f. of hydrogen per barrel of hydrocarbon, through thedesulfurization zone wherein the naphtha and gas-oil are simultaneouslydesulfurized, denitrogenated, and deoxygenated to produce respectively,hydrogensulfide, ammonia, and water vapor. The hydrocarbons remainingare hydrogenated to stable hydrocarbon products maintaining a highliquidproduct yield. These reactions. consume the excess hydrogen which wasgenerated as described during the reforming step. In doing so,considerable heat is liberated and accordingly the reactant mixture ispreferably cooled at one or more points along the length of thedesulfurization zone so as to maintain the-optimum desulfurizationtemperature.

In a preferred modification of the operation of this process, thenaphtha and gas-oil feed rates are balanced against one another asafunction of the naphthene hydrocarbon content of the gasoline and ofthe sulfur, nitrogen, and oxygen content of the gas-oil so that duringthe reforming step the naphthene dehydrogenation proceeds sufiicientlyto liberate .a quantity of hydrogen which is equal to or greater thanthat necessary to fully desulfurize, denitrogenate, and deoxygenate boththe gas-oil and the naphtha. Thus a hydrogen balance is reached and nooutside sources of hydrogen are required. This is one of the advantagesof the present invention which, together with the requirement of only asingle catalyst, namely cobalt molybdate, the means fortemperaturecontrol in the desulfurizatibn and reforming zones, the useof separate cobalt molybdate catalyst streams within a single contactingzoneto treat two hydrocarbon streams, the naphtha stripping of thecombined .catalyst streams to permit total recovery of gas-oil therebyeliminating the usual 10% gas-oil loss, and; the subsequent steamstripping of the spent catalyst to recover the naphtha therefrom, yieldsan integrated process which permits simultaneous treatment of tworelated hydrocarbon fractions to produce premium-grade internalcombustion engine fuels. By locating the desulfurization zone above thereforming zone and subsequently passing the spent desulfurizationcatalyst stream through the reforming zone, either directly orindirectly, the temperature of the spent desulfui ization catalyst israised in the presence of a naphtha and hydrogen flow which has beenfound to permit the highly efficient stripping of gas-oil from thecatalyst with substantially no lossdue to catalytic cracking. In themodification shown in the figure wherein spent catalyst from thedesulfurization zone passes indirectly through the reforming zone, thesame effect results in a that the catalyst is gradually heated withinthe tubes and in the presence of a small countercurrent flow of naphthaand. hydrogen which passes upwardly therethrough.

Themixture of gas-oil, naphtha, and hydrogen is removed from the reactorefliuent at the top of the contacting zone, cooled, partially condensed,and the vapor remaining is separated from the liquid. The gas fractioncontains recycle hydrogen together with hydrogen sulfide, ammonia, andwater vapor which may be separated from the recycle hydrogen byconventional means. It is preferred that the hydrogen recycle contain atleast 25% hydrogen by volume and preferably more than 70% hydrogen byvolume. The liquid fraction comprises a mixture of naphtha and gas-oilwhich is substantially free of sulfur, nitrogen, and oxygen and thenaphtha fraction of which consists essentially of branched chainparaffin hydrocarbons and aromatic hydrocarbons and is an excellentblending stock for premium and aviation gasolines.

In the process of the present invention, it has been found that therequired catalyst recirculation is low and the permissible on-streamtime of the catalyst is long and therefore the regeneration of thecatalytic material is quite simple. Although the spent catalyst removedfrom the bottom of the contacting zone may be passed through a separateregeneration zone in which the solids flow downwardly as a moving bed,it is a preferred form of this invention to convey the granular solidsfrom the bottom to the top of the column through an elongated conveyanceconduit in which the granular solids are maintained in compactdense-packed form, that is, as a mass having a bulk densitysubstantially equal to the static bulk density of the solids when atrest. The conveyance fluid employed is a regeneration gas such as amixture of flue gas to which air or oxygen has been added to produce aregeneration gas mixture containing between about 1% and about 5% oxygenby volume at the bottom of the lift line. This combinationconveyanceregeneration gas is passed through the conveyance zone at arate suflicient to convey the granular solids upwardly as a compactmass. The fluid and the solids flow concurrently at a relatively lowrate and are regenerated during conveyance. The spent regeneration gasesare removed at the top of the conveyance conduit, and the regeneratedsolids are circulated into the top of the contacting zone.

It has been found that in spite of the regeneration of the catalyst,from 20 to 40% of the sulfur present on the spent catalyst remains,possibly in the form of cobalt or molybdenum sulfides or the like, theconstitution of which is not known. It has been determined that whensuch regenerated catalyst is introduced directly into thedesulfurization zone and contacts the hydrogen sulfidecontaining gasthere, the hydrogen sulfide in some way reacts with the sulfidedregenerated catalyst to produce elemental sulfur. This sulfur is carriedout with the reactor eflluent and renders the product sour andcorrosive. It has been found that by treating the regenerated catalystwith a countercurrent stream of hydrogen recycle gas substantially freeof hydrogen sulfide, the sulfur on the catalyst is liberated as sulfurand sulfur dioxide in a reaction generating considerable heat, and thepresence of elemental sulfur in the product is fully eliminated. Thecharacter of the reaction is not fully understood, but its effect uponthe physical properties of the product is remarkable for the efliuentgasoline is sweet.

The conveyance of spent catalyst to a separate regeneration zone and itsregeneration therein during downward flow therethrough as a moving bedis conventional and will not be described in further detail. However,the modification wherein the spent catalyst is conducted upwardly as amoving bed through a conveyance-regeneration zone is a novel type ofregeneration and the details of its operation will be briefly describedbelow.

The pressure drop characteristic of this type of solids conveyance is ofthe order of 100 times that characteristic of pneumatic or gas lift(suspended) solids conveyance and the volume of gas required to conveydensepacked solids is only a few percent of that required in gas lift.The granular solids to be conveyed are removed from the bottom of thecontacting column at substantially the reforming pressure, are passedthrough a solids pressuring zone to increase'the pressure of gases associated with the solids by an amount substantially equal to thecharacteristic pressure drop of the conveyance conduit, and then thesolids are passed into the conveyance element of the apparatus.

The inlet of the conveyance-regenerator conduit is thus maintained at arelatively higher pressure generally than the pressure of the solidsbefore introduction into the conveyance conduit. The granular solids arethen transferred through the conveyance conduit in compact dense packedform by means of a concurrently depressuring conveyance-regenerationfluid. The frictional forces generated by the fluid depressuring throughthe interstices of the compact mass of solids generate a pressuregradient in the conduit sufiicient to counteract opposing forces offriction of the solids sliding against the walls of the conduit as wellas the opposing force of gravitation and thereby establish a conveyingforce permitting movement of the compact porous granular mass in thedirection of decreasing conveyance fluid pressure when solids areremoved from the outlet and fed into the inlet.

The depressuring conveyance fluid generates a pres sure drop per unitlength of conduit i l dl (the pressure gradient) sufiicient to overcomethe opposing gravitational force (p cos 0), wherein p is the bulkdensity of the dense-packed granular solids and 0 is the angulardeviation of the conveyance conduit from the vertical. The ratio of theformer to the latter is p 'cos 6 i 1 This factor is termed theconveyance force ratio and is the ratio of the force tending to move thesolids through the conveyance conduit to the opposing forces of gravitytending to restrain such flow. The conveyance fluid must be depressuredthrough the conduit at a rate suflicient to raise the conveyance forceratio to a value greater than 1.0 (factors in consistent units) in orderthat the conveying force exceed the forces resisting flow. The amount bywhich the conveyance force ratio must exceed a value of 1.0 is equal tothe magnitude of the friction forces also tending to resist solids flow.

The granular solids are maintained during conveyance and regeneration inthe compact form by means of the application of a compressive force onthe discharge solids issuing from outlet of the conveyance conduit.Various means are available for applying such a force which has theeffect of restricting the discharge rate of granular solids from theconveyance conduit but has virtually no effect on the discharge of theconveyance fluid therefrom. A transverse thrust plate or a grid may bespaced opposite and adjacent the outlet opening and against which themass of solids discharges, or a static bed of solids may beused tosubmerge this outlet. The rate of solids conveyance is determined by therate of solids removal from the contacting column which is full ofdense-packed solids in the form of a moving bed. The solids feeder atthe column bottom controls'this variable as described below. The presentinvention will be more clearly understood by reference to theaccompanying drawings in which:

Figure 1 is a schematic flow diagram of the process of this inventionincluding an elevation view in cross section showing the details of thecontacting column,

Figure 2 shows a cross-sectional view of the detail of the top part ofthe structure of Figure 1.

Referring now more particularly to Figure 1, contacting column 10 isdivided into three major contacting zones including first treating ordesulfurization zone 12, second treating or reforming zone 14, andcombination third treating or reforming and stripping zone 16.

Contacting column 10 is provided at successively lower levels thereinwith treating gas injection zone 96, hopper and seal zone 18, efiluentdisengaging zone 20, second desulfurization zone 22, cooling zone 24,first desulfurization zone 26, gas-oil engaging and naphtha mixing zone28, third reforming zone 32, heating zone 34, second reforming zone 36,first and second catalyst stream rate control zone 38, first reformingand naphtha stripping zone 40, naphtha engaging zone 42, hydrogenstripping zone 43, hydrogen engaging zone 44, stripping zone 45,stripping gas engaging zone 46, and catalyst feeder zone 48.

The granular catalyst introduced into hopper zone 18 through inlet 94passes entirely through desulfurization zone 12 as a downwardly movingbed by gravity. The spent catalyst is divided at the bottom of thedesulfurization 'zone into a primary and secondary portion just abovethe point of gas-oil injection through line 208 into engaging zone 28.The primary portion passes downwardly directly into and throughreforming zone 14 and is removed therefrom through conduits 58 at a ratecontrolled by valves 60. The secondary portion is bypassed indirectlythrough and in indirect heat exchange relationship to reforming zone 14through secondary tubes 54 at a rate controlled by valves 56. The spentcatalyst is combined into a single stream prior to passage through firstnaphtha reforming and stripping zone 40 in which the fresh naphtha feedthoroughly strips any residual gas-oil from the catalyst picked upduring passage through the desulfurization zone. It is not necessarythat thesecontrol elements be valves, for orifices of fixed or variablearea may be substituted at this point in the apparatus so as to controlthe relative solids flow rate. Orifices are entirely effective since theflow of solids through an orifice is substantially unaffected by thedepth of the bed of solids above the orifice provided this depth isgreater than two or three orifice diameters. Since the flow of solidsthrough an orifice is inhibited by countercurrent fluid flowtherethrough, vapor risers and caps 62-are provided which effectivelybypass the reactant naphtha through caps 62 thus preventing any vaporflow interference with the solids flow in conduits 58.

The absolute circulation rate of granular solids through column-10 isfixed by reciprocating tray solids feeder 48 located in the bottom ofthe column. The details of this apparatus element are not shown becausethey are wellknown in the art. This element also provides for a uniformremoval of spent catalyst throughout the entire cross-sectional area ofthe column and this uniformity of solids flow isreflected entirelythroughout the height of the column when primary tubes 58, secondarytubes 54, and the other tubular elements of this apparatus are uniformlydistributed throughout the cross-sectional area of the column.

The combined stream of spent granular solids passes downwardly intosolids pressuring means 66 in which the spent granular catalyst ispressured from the reaction pressure to a higher pressureexceeding thereaction pressure by an amount substantially equal to the requiredpressure diiferential for conveying the spent catalyst as asubstantially compact upwardlymoving bed through conveyance-regenerationconduit 68. Thedetails of solids pressuring means 66 are notshown forthey are described in copending application Serial No. 217,337, filedMarch 24, 1951, now U .S. Patent No. 2,695,212. The spent catalyst ispressured by means of high pressure gas, preferably inert such asoxygen-free flue gas, introduced through line 70 controlled by valve 72.The thus pres- "sured"solids then arepa'ssed downwardly to submergeinlet opening 74 of theconveyance regeneration zone. A

conveyance-regeneration gas, containing between about 1% and about 5% byvolume of oxygen, is introduced through line 76 at a rate controlled byvalve 78 and passes downwardly concurrently with the pressured spentcatalyst which flows by gravity into inlet opening 74, or the oxygenconcentration in line 68 may be maintained by injection of the oxygencontaining gas directly into the line as through line 71 controlled byvalve 73. This conveyance-regeneration fluid is depressured concurrentlythrough conveyance-regeneration zone 68 as described above and the spentcatalyst is simultaneously conveyed and regenerated during transitupwardly through the conveyance-regeneration zone. In the presentprocess, the catalyst circulation rate is quite low and the heatgenerated by regeneration may be carried out of the system with thespent regeneration gases as subsequently described, or a jacket orvessel may be provided surrounding conveyance zone 68 whereby a coolantmay be passed around zone 68 to remove heat in this way.

The spent regeneration gases discharging from zone 68 with theregenerated solids preferably contain less than 1% oxygen. Theregenerated catalyst discharges into solids-receiving and elutriationzone 80 directly against bafiie 82 whereby the solids thrust orcompacting force is applied to the discharging catalyst preventing itsfluidization and maintaining the granular solids during conveyance andregeneration at a bulk density substantially equal to the bulk densityof the downwardly moving beds of catalyst in contacting column 10. Thespent regeneration gas is disengaged from the solids through inclinedsurface 87 of the discharged solids and is removed from the top ofsolids-receiving zone 80 through outlet 81 and aperture 83 and line 84at a rate controlled by valve 86 which is actuated by back pressureregulator 88. These gases, in being disengaged from the dischargedsolids, act as an elntriation medium and suspend and carry out solidsfines. The degree of elntriation is variable, as described in connectionwith Figure 2 by varying the area open to gas disengagement. Theregeneration elntriation gas is removed at substantially the samepressure as the operating pressure in contacting column 10, and may berepressured and recirculated through the regeneration zone with addedoxygen.

Referring now to Figure 2, a plan view in cross section ofsolids-receiving chamber 80 is shown. Herein are shown the crossedvertical bafiies 79 extending downward into the discharged solidsforming 4, 6, 8, or more individual circularly disposed elntriationchambers of pie-shaped cross section. Only 4 chambers are shown forpurposes of illustration. Gas outlet 81 is provided centrally, betweenthe individual chambers, and is provided with one or more openings 83.Thus, with one such opening, only the solids disengaging area in oneindividual chamber is active and the gas velocity therein is relativelyhigh because of the relatively constant conveyance-regeneration gas flowthrough the lift line and the thus reduced area of solids through whichit is disengaged. By using more such openings, more of the individualelntriation chambers actively disengage gas and the disengagementvelocity is lower. With the greater velocities of disengagement largersolids fines are suspended and carried out, and reductions in velocityas described reduce the size of the particles suspended and removed.

The regenerated cobalt moly'bdate catalyst, freed of solids fines,passes downwardly in the form of compact bed 90 downwardly over treatinggas disengaging zone 92 and then downwardly through inlet conduit 94into the top of column 10. The lower opening of inlet 94 is surroundedby treating gas injection collar 96. Hydrogen sulfide-free recyclehydrogen is introduced by means of line 98 at a rate controlled by valve100 and flow recorder controller 102 into collar 96. This treating gassplits into two streams, the first passing downwardly concurrently withthe catalyst through hopper zone 18, and the second passing upwardlythrough inlet 94 and through treating zone 104 in the lower portion ofsolids-receiving zone 80. This latter hydrogen stream countercurrentlycontacts the regenerated catalyst, causes the liberation therefrom ofthe residual quantities of sulfur in the form of sulfur and sulfurdioxide which are removed from treating gas disengaging zone 92 throughline 106 at a rate controlled by valve 108 in accordance withdifferential pressure controller 110 which maintains a positive pressuredifferential between the extremities of inlet zone 94. This differentialpressure is quite small, of the order of a few inches of water andserves to seal the top of the column against hydrogen sulfide contactingthe regenerated catalyst. In this manner the reactor effluent ismaintained entirely free of elemental sulfur and in this way a longstanding problem has been eliminated whereby the conventional posttreating operations on the product to render it sweet and non-corrosiveare avoided.

The remainder of the description of Figure 1 will be conducted as anillustrative example in which a straight run naphtha and a straight rungas-oil are simultaneously treated by the process of this invention.Both the naphtha and the gas-oil are heavily contaminated with sulfurand nitrogen and their physical properties are as follows:

TABLE 1 Naphtha feed Gravity, API 49.8 Boiling range, F 200-400 Sulfur,weight percent 0.10 Nitrogen, weight percent 0.003 Knock rating, F-lClear 57 TABLE 2 Gas-oil feed Gravity, API 24.5 Boiling range, F.500-900 Sulfur, weight percent 3.76 Nitrogen, weight percent 0.24

The naphtha feed rate is 1000 barrels per day and the gas-oil feed rateis 500 barrels per day. The total catalyst circulation rate is 14 tonsper day, the rate through the desulfurization zone being 14 tons perday, and the rate through the reforming zone being tons per day. Thedesulfurization and reforming zones are operated at a pressure of about400 p.s.i.a. (pounds per square inch ab;

solute), the temperature of the reforming zone is maintained at anaverage of 900 F. and the temperature of the desulfurization zone ismaintained at an average of 750 F.

The naphtha feed passes from storage through line 120 by means ofnaphtha feed pump 122 at the above-mentioned rate controlled by valve124 and flow recorder controller 126 through line 128 and interchanger130. Herein the cold feed is exchanged with part of the reactor efiluentdescribed below and is raised to a temperature of 600 F. The preheatednaphtha then flows through line 132 through naphtha preheating andvaporizing coil 134 in furnace 136. The naphtha vapor then passes bymeans of line 138 into naphtha engaging zone 42.

Recycle hydrogen, necessary in the operations conducted in this processand separated from the reactor effluent as described below, flowsthrough line 140 into gas purifier 142. Herein, by conventional means,hydrogen sulfide, ammonia, and water vapor are separated from therecycle gas and if desired any low molecular weight hydrocarbon gaswhich may be present such as methane, ethane, and the like may also beremoved through line 143. The hydrogen thus treated then flows throughline 144 together with additional hydrogen, if necessary, injectedthrough line 146 controlled by valve 148 and is pumped by means ofrecycle blower 150 at a rate controlled by valve 152 and fiow recordercontroller 154 through hydrogen heating coil 156 in furnace 136. Theheated hydrogen, at a temperature of about 900 F.

10 passes through line 158 at a rate of 3000 M s.c.f./d. (thousandstandard cubic feet per day) into hydrogen recycle engaging zone 44.Under the influence of a seal or stripping gas such as steam introducedthrough line 160 controlled by valve 162 into engaging zone 46 at'aslightly higher pressure, substantially all of the hydrogen recycle gaspasses upwardly from zone 44 and is combined with naphtha vapor inengaging zone 42 to form a reactant naphtha and hydrogen mixture whichpasses through the reforming zone as described in detail below.

The reactant mixture of naphtha and hydrogen passes upwardly throughfirst reforming and naphtha stripping zone 40 countercurrent to thecombined catalyst streams. Herein the initial catalytic reforming of thenaphtha takes place simultaneously with exothermic hydrogenation of anyolefinic constituents in the naphtha feed. The temperature risessomewhat to values preferably not exceeding about 925 F. This maximumtemperature is controlled by reducing the naphtha vapor inlettemperature so that olefin hydrogenation does not raise the temperatureabove a value of that given. Simultaneously in zone 40, a highlyeffective naphtha and hydrogen stripping of that part of the catalystintroduced thereinto from desulfurization zone 12 takes place.Substantially all of the residual gas-oil present on the catalyst isre.- moved thereby and vaporized leaving a spent reforming catalystcontaining traces of adsorbed naphtha but substantially gas-oil free. Asstated above, this spent catalyst is steam stripped in zone 45immediately above stripping gas engaging zone 46 and the naphtha isreturned upwardly into the reactant mixture and passes upwardlytherewith. In this manner substantially no gasoil or naphtha feed islost by oxidation in the spent catalyst regeneration step and maximumliquid product yields of the order of 95% to 99% are obtained.

The reactant mixture of naphtha and hydrogen, to gether with minoramounts of gas-oil vapor stripped from the catalyst, passes upwardlythrough vapor risers and caps 62 into and countercurrently throughsecond reforming zone 36. Herein additional aromatization takes placecausing the temperature to drop to a value of preferably not less than875 F. by the time it reaches heating zone 34.

At this point the naphtha reactants are reheated to a temperature ofabout 900 F. or slightly higher for subsequent passage through thirdreforming zone 32. Preferably the disengaging-engaging structure shownin the drawing is employed which consists of upper tray 166, lower tray168 with a plurality of seal tubes 170 open at both ends and extendingfrom above tray 166 through and to a point below lower tray 168. Sealtubes 170 pass the catalyst downwardly therethrough creating a pathhaving a relatively high resistance to reactant vapor flow. Accordinglyonly a minor portion of the reactant vapor mixture passes upwardlythrough tubes 170 generating a pressure differential of about 1.0 p.s.i.which is sufiicient to force the major portion of the mixture from lowerdisengaging Zone 172 through line 174, into and through interheater 176wherein the temperature is increased to compensate for the temperaturedrop occasioned by endothermic reforming reactions in reforming zone 36and the prospective temperature drop in zone 32. The reheated mixture isthen passed through line 178 into engaging zone 180 wherefrom it passesupwardly through vapor risers 182 into the bottom of third reformingzone 32.

Herein the reheated vapor mixture contacts reforming catalyst andadditional aromatization takes place causing a further temperaturedecrease. The naphtha reforming zone effluent, containing aromatizednaphtha vapor together with an excess of hydrogen produced during thereforming, is disengaged from the catalyst in zone 28. Fresh gas-oil,injected as described below, is mixed herein with the naphtha effluentfrom reforming third zone 32 and passes upwardly through vapor risersand caps 210 to be treated simultaneously in desulfurization zone 12.

i The gas-oil to be converted is introduced through line 188 and pumpedby means of pump 190 at a rate of 500 barrels per day controlled byvalve 192 and flow recorder controller 194. The gas-oil flows throughline 196 through preheater 198 in exchange with the remaining part ofthe reactor eflluent. The preheated gas-oil at a temperature of about650 F. flows through line 200 into and through gas-oil heating andvaporizing coil 202 in furnace 204. Herein a partial or completevaporization of gas-oil is effected, depending upon its end point, andthe gas-oil is combined in mixing zone 28 with the naphtha-hydrogeneffluent from reforming Zone 14. The

- furnace 204 is controlled to have an outlet temperature such that uponadmixture of the thus heated gas-oil with the effluent naphtha vaporflowing from third reforming zone 32, the temperature of the resultingmixture is substantially equal to the preferred desulfurizationtemperature, that is, about 750 F. In the present example the furnaceoutlet temperature was about 650 F. and the temperature of the naphthamixture flowing into mixing zone 28 from reforming zone 32 was 900 F.

If it is desired, better mixing of the naphtha and gasoil vapor to bedesulfurized may be obtained by removing the disengaged naphtha andhydrogen from the column, mixing this stream with the gas-oil at a pointoutside the column, and returning the mixture to the bottom of thedesulfurization zone for passage therethrough;

The reactant mixture of naphtha and gas-oil vapor and recycle hydrogenformed as above described passes upwardly from engaging zone 28 throughvapor risers 210 and then through first desulfurization zone 26countercurrent to the downwardly flowing stream of cobalt molybdatecatalyst. Herein, under the temperature and pressure conditions given,the sulfur, nitrogen, and oxygen compounds are destructivelyhydrogenated forming the corresponding hydrocarbon derivatives togetherwith hydrogen sulfide, ammonia, and water vapor. Depending upon theextent of gas-oil and naphtha contamination with these compounds, moreor less heat is liberated in first desulfurization zone 26 and thetemperature of the reactant vapor mixture rises to a value of about 780F. after passage therethrough. In a manner entirely analogous to thedisengaging and engaging of the reactant naphtha vapor described inconnection with heating zone 34, the reactant mixture is disengaged,cooled, and engaged in cooling section 24. This section is provided withupper tray 212 and lower tray 214 forming disengaging zone 216 andengaging zone 218. Catalyst seal tubes 220 are equivalent to tubes 170described above. As before, a minor portion of the reactant vapor passesupwardly through the restricted passageway formed by tubes 220generating a pressure drop which forces the major portion fromdisengaging zone 216 through line 221 and intercooler 222 and then backthrough line 224 into engaging zone 218. In this example intercooler 222serves to decrease the temperature of the reactant mixture to about 750F. at which it enters second desulfurization zone 22 through vaporrisers hopper zone 18. The reactor eflluent includes the naphtha andgas-oil vapors substantially free of the aforementioned contaminantstogether with moderate amounts of hydrogen sulfide, ammonia, watervapor, hydrogen, and small amounts of low molecular weight hydrocarbongases,

ordinarily divided into two streams.

employed in the process as described above.

The reactor effluent passes from disengaging zone 20 through line 228,and is divided into two streams which pass through gas-oil preheater 198and through naphtha preheater 130. Efliuent cooling and condensationtakes place and then the combined streams pass through line 230 throughproduct effluent cooler 232 and through line 234 into vapor liquidseparator 236.

The condensed liquid product accumulates in the lower portion ofseparator 236 and is removed therefrom through line 238 controlled byvalve 240 and liquid level controller 242. This liquid product containssome water and consists essentially of gas-oil and naphtha mixture. Bymeans of conventional techniques the water is separated as by settlingand decantation and the hydrocarbon product is fractionated into agasoline fraction and a desulfurized gas-oil fraction having excellentcracking qualities and containing a large fraction of hydrocarbonssuitable for 50 cetane diesel fuel or jet engine fuel. Upon suchfractionation 952 barrels per day of C -free reformed gasoline having a400 F. end point are obtained, amounting to a liquid naphtha yield of95.2%. The physical properties of this gasoline are as follows:

TABLE 3 Reformed gasoline product Gravity, API 50.4 Boiling range, F-420 Sulfur, weight percent. 0.002 Nitrogen, weight percent. Nil Knockrating, F-l Clear 85.2 Knock rating, 3 ml. TEL 91.8

Sulfur, weight percent 0.53 Nitrogen, weight percent 0.10 Cetane No 38.0

.The uncondensed portion of the reactor effluent is removed fromseparator 236 through line 244 and is The first stream passes throughline to provide the recycle hydrogen Any net production of hydrogen,which may result when highly naphthenic gasolines are reformed anddesulfurized in the presence of a gas-oil which either containsrelatively small amounts of sulfur or which isfed to the system atrelatively low rates, is bled from the system through line246 at a ratecontrolled by valve 248 and back pressure regulator 250 which maintainsthe operating pressure onthe system. In the present example, therelative feed rates and compositions were such that no net hydrogen isproduced and no net consumption of hydrogen takes place.

In this invention the desulfurization, which term is 'used to includedenitrogenation and deoxygenation, takes place in the upper portion ofthe contacting column and the naphtha reforming is effected in the lowerportion of the column. In the process, one or more interheaters orintercoolers are employed in the reforming or desulfurization zonesrespectively depending upon the degree of uniformity of the reactiontemperature desired. Only one inter-cooler and interheater has beenshown and described, but it should be understood that as many as 8 or 10.ofsuch heaters can be employed in the present apparatus.

Although other catalysts having desulfurization and reforming activitiesmay be employed or a mixture of ,known catalysts including adesulfurization catalyst and a reforming catalyst can 'also be used, thepreferred catalytic agent to be used in this process is the cobaltmolybdate type containing cobalt and molybdenum oxides in the amountsgiven above because these have been found to be extremely stable underreforming and desulfurization conditions and in addition have been foundto have very high activities for reforming, desulfurization,denitrogenation, and deoxygenation properties which are not found inother known catalysts.

Cobalt molybdate catalysts in general comprise mixtures of cobalt andmolybdenum oxides wherein the molecular ratio of C to M00 is betweenabout 0.4 and 5.0 and are prepared as described below. This catalyst maybe employed in unsupported form or alternatively it may be distended ona suitable carrier such as alumina, silica, zirconia, thoria, magnesia,magnesium hydroxide, titania or any combination thereof. Of theforegoing carriers it has been found that the preferred carrier materialis alumina and especially alumina containing about 3-8% by weight ofsilica.

In the preparation of the unsupported cobalt molybdate, the catalyst canbe coprecipitated by mixing aque ous solutions of, for example, cobaltnitrate and ammonium molybdate, whereby a precipitate is formed. Theprecipitate is filtered, washed, dried and finally activated by heatingto about 500 C.

Alternatively, the cobalt molybdate may be supported on alumina bycoprecipitating a mixture of cobalt, aluminum and molybdenum oxides. Asuitable hydrogel of the three components can be prepared by adding anammonical molybdate solution to an aqueous solution of cobalt andaluminum nitrates. The precipitate which results is washed, dried andactivated.

In still another method, a washed alumina hydrogel is suspended in anaqueous solution of cobalt nitrate and an ammoniacal solution ofammonium molybdate is added thereto. By this means a cobalt molybdategel is precipitated on the alumina gel carrier.

Catalyst preparations similar in nature to these and which can also beemployed in this invention have been described in US. Patents 2,369,432and 2,325,033.

Still other methods of catalyst preparation may be employed such as byimpregnating a dried carrier material, e.g. an alumina-silica gel, withan ammoniacal solution of cobalt nitrate and ammonium molybdate.Preparations of this type of cobalt molybdate catalyst are described inU.S. Patent 2,486,361.

In another method for preparing impregnated molybdate catalyst thecarrier material may be first impregnated with an aqueous solution ofcobalt nitrate and thereafter impregnated with an ammoniacal molybdate.Alternatively, the carrier may also be impregnated with these solutionsin reverse order. Following the impregnation of the carrier by either ofthe foregoing methods the material is drained, dried and finallyactivated in substantially the same manner as is employed for the othercatalysts.

In the preparation of impregnated catalysts where separate solutions ofcobalt and molybdenum are employed, it has been found that it ispreferable to impregnate the carrier first with molydenum, e.g.,ammoniacal ammonium molybdate, and thereafter to impregnate with cobalt,e.g., aqueous cobalt nitrate, rather than in reverse order.

In another method for the preparation of suitable catalyst, a gel ofcobalt molybdate can be prepared as described hereinbefore for theunsupported catalyst, which gel after drying and grinding can be mixedwith a ground alumina, alumina-silica or other suitable carrier togetherwith a suitable pilling lubricant or binder which mixture can then bepilled or otherwise formed into pills or larger particles and activated.

In another modification, finely divided or ground molybdic oxide can bemixed with suitably ground carrier such as alumina, alumina-silica andthe like in the presence of a suitable lubricant or binder andthereafter pilled or otherwise formed into larger agglomeratedparticles. These pills or particlesare then subjected to a preliminaryactivation by heating to 600 C. for example, and are thereafterimpregnated with an aqueous solution of cobalt nitrate to deposit thecobalt compound thereon. After draining and drying, the particles areheated to about 600 C. to form the catalyst.

It is apparent from the foregoing description of the different types ofcobalt molybdate catalyst which may be employed in this invention thatwe may employ either an unsupported catalyst, in which case the activeagents approximate of the composition, or we may employ a supportedcatalyst wherein the active agents, cobalt and molybdenum oxides, willgenerally comprise from about 7 to 22% by weight of the catalystcomposition. In all of the foregoing catalytic preparations it isdesirable to maintain the molecular ratio of cobalt oxide as C00 tomolybdic oxide as M00 between about 0.4 and 5.0.

A particular embodiment of the present invention has been described inconsiderable detail by way of illustration. It should be understood thatvarious other modifications and adaptations thereof may be maintained bythose skilled in the particular art without departing from the, spiritand scope of this invention as set forth in the appended claims.

I claim:

1. In a moving-bed isobaric catalytic contacting process whereingranular reforming and desulfurization catalyst is circulated downwardlythrough an upper lowtemperature desulfurization zone and then through asubjacent high-temperature reforming zone, and wherein naphtha plushydrogen is contacted countercurrently with the catalyst in saidreforming zone, and the reformed naphtha is then admixed with a gas oiland the resulting mixture of gas oil, naphtha and hydrogen is thenpassed upwardly through said desulfurization zone to effectdesulfurization, the improved method for obtaining controlled relativecatalyst treating capacity in each of said contacting zones while stilleffectively utilizing said naphtha feed to strip residual gas oil fromall of said catalyst prior to regeneration, which comprises passing acontrolled first portion of the catalyst from said desulfurization zonethrough the upper major portion of said reforming zone in indirectheat-exchange therewith and out of contact with the major stream ofnaphtha flowing therethrough, passing the remainder of said catalystfrom the desulfurization zone through the entire reform ing zone incontact with said naphtha, and recombining said first portion ofcatalyst with said remainder of catalyst in the lower portion of saidreforming zone, whereby the relative amount of catalytic reformingcapacity is readily controllable in response to variations in quantityand nature of feeds, and the entire catalyst stream is effectivelystripped of residual gas oil by the naphtha and hydrogen vapors in saidlower portion of the reforming zone.

2. A process as defined in claim 1 wherein the temperature profile insaid reforming zone is maintained relatively uniform by withdrawingreactant naphtha vapors therefrom at at least one intermediate pointalong the length thereof, heating said withdrawn portion to the desiredreforming temperature, and then reintroducing the reheated vaporsdownstreamwardly in said reforming zone.

3. A process as defined in claim 1 wherein the quantity of said firstportion of catalyst which is diverted through the reforming zone inindirect heatexchange therewith is controlled to provide approximatelythe necessary reforming capacity per hour in said remaining stream ofcatalyst to effect suflicient reform ing and net hydrogen production tobalance approxi- 15 mately the net hydrogen consumption in saiddesulfurization zone.

4. A process as defined in claim 1 wherein said catalyst consistsessentially of a minor proportion of cobalt oxide plus molybdenum oxidesupported on a carrier which is predominantly activated alumina.

5. A process as defined in claim 1 wherein said desulfurization zone ismaintained at a temperature between about 575 and 900 F., and saidreforming zone is maintained at a temperature between about 800 and 1000F., and wherein both of said Zones are maintained at substantially thesame pressure within the range of about 50 to 5,000 p.s.i.g.

6. A process as defined in claim 1 wherein said first portion ofcatalyst is passed through said reforming zone by means of at least onevertical conduit extending through the upper portion of said reformingzone.

7. A process as defined in claim 1 wherein the combined strippedcatalyst from said reforming zone is subjected to oxidative regenerationand then recycled to said desulfurization zone.

8. A process as defined in claim 7 wherein said regeneration isefi'ected in a compact-flow lift line simultaneously with the conveyancethereof by the use of oxygen-containing lift gas at regenerationtemperatures.

9. In a moving-bed isobaric catalytic contacting process whereingranular reform-ing and desulfurization catalyst is circulateddownwardly through an upper lowtemperature desulfurization zone and thenthrough a subjacent high-temperature reforming zone, and wherein alow-boiling hydrocarbon plus hydrogen is contacted countercurrently withthe catalyst in said reforming zone to effect reforming with a netproduction of hydrogen,

and the reformed product is then admixed with a highboiling hydrocarbonand the resulting mixture containing hydrogen is then passed upwardlythrough said desulfurization zone to effect desulfurization, theimproved method for obtaining controlled relative catalyst treatingcapacity in each of said contacting zones while still efiectivelyutilizing said low-boiling hydrocarbon feed to strip residualhigh-boiling hydrocarbon from all of said catalyst prior toregeneration, which comprises passing a controlled first portion of thecatalyst from said desulfurization zone through the upper major portionof said reforming zone in indirect heat-exchange therewith and out ofcontact with the major stream of low-boiling hydrocarbon flowingtherethrough, passing the remainder of said catalyst from thedesulfurization zone through the entire reforming zone in contact withsaid low-boiling hydrocarbon, and recombining said first portion ofcatalyst with said remainder of catalyst in the lower portion of saidreforming zone, whereby the relative amount of catalytic reformingcapacity is readily controllable in response to variations in quantityand nature of feeds, and the entire catalyst stream is effectivelystripped of residual high-boiling hydrocarbon by the low-boilinghydrocarbon vapors and hydrogen in said lower portion of the reformingzone.

References Cited in the file of this patent UNITED STATES PATENTS1,264,024 Davis Apr. 23, 1918 2,091,514 Meston Aug. 31, 1937 2,253,486Belchetz Aug. 19, 1941 2,293,759 Penisten Aug. 25, 1942 2,393,288 ByrnsJan. 22, 1946 2,409,353 Giuliani Oct. 15, 1946 2,439,372 Simpson Apr. 6,1948 2,450,724 Grote Oct. 5, 1948 2,451,924 Crowley Oct. 19, 19482,459,824 Leffer Jan. 25, 1949 2,466,005 Crowley Apr. 5, 1949 2,490,336Crowley Dec. 6, 1949 2,494,794 Bonnell Jan. 17, 1950 2,543,005 EvansFeb. 27, 1951 2,558,769 McKinney July 3, 1951 2,594,289 Caldwell Apr.29, 1952 2,606,861 Eastwood Aug. 12, 1952 2,684,390 Bills July 20, 19542,758,059 Berg Aug. 7, 1956 2,791,544 Eastwood May 7, 1957 OTHERREFERENCES New Lift Technique, Weber, Oil and Gas Journal, August 11,1952, p. 75.

1. IN A MOVING-BED ISOBARIC CATALYST CONTACTING PROCESS WHEREIN GRANULARREFORMING AND DESULFURIZATION CATALYST IS CIRCULATED DOWNWARDLY THROUGHAN UPPER LOWTEMPERATURE DESULFURIZATION ZONE AND THEN THROUGH ASUBJACENT HIGH-TEMPERATURE REFORMING ZONE, AND WHEREIN NAPHTHA PLUSHYDROGEN IS CONTACTED COUNTERCURRENTLY WITH THE CATALYST IN SAIDREFORMING ZONE, AND THE REFORMED NAPHTHA IS THEN ADMIXED WITH A GAS OILAND THE RESULTING MIXTURE OF GAS OIL, NAPHTHA AND HYDROGEN IS THENPASSED UPWARDLY THROUGH SAID DESULFURIZATION ZONE TO EFFECTDESULFURIZATION, THE IMPROVED METHOD FOR OBTAINING CONTROLLED RELATIVECATALYST TREATING CAPACITY IN EACH OF SAID CONTACTING ZONE WHILE STILLEFFECTIVELY UTILIZING SAID CATAYLST PRIOR TO REGENERATION, WHICHCOMPRISES PASSING A CONTROLLED FIRST PORTION OF THE CATALYST FROM SAIDDESULFURIZATION ZONE THROUGH THE UPPER MAJOR PORTION OF SAID REFORMINGZONE IN INDIRECT HEAT-EXCHANGE THEREWITH AND OUT OF CONTACT WITH THEMAJOR STREAM OF NAPHTHA FLOWING THERETHROUGH, PASSING THE REMAINDER OFSAID CATALYST FROM THE DESULFURIZATION ZONE THROUGH THE ENTIRE REFORMINGZONE IN CONTACT WITH SAID NAPHTHA, AND RECOMBINING SAID FIRST PORTION OFCATALYST WITH SAID REMAINDER OF CATALYST IN THE LOWER PORTION OF SAIDREFORMING ZONE, WHEREBY THE RELATIVE AMOUNT OF CATALYST REFORMINGCAPACITY IS READILY CONTROLLABLE IN RESPONSE TO VARIATIONS IN QUANTITYAND NATURE OF FEEDS, AND THE ENTIRE CATALYST STREAM IS EFFECTIVELYSTRIPPED OF RESIDUAL GAS OIL BY THE NAPHTHA AND HYDROGEN VAPORS IN SAIDLOWER PORTION OF THE REFORMING ZONE.